Steel stud frame type curtain walls have been conventionally known to comprise a thin, large, exterior curtain wall, this type of curtain wall being constituted in such a manner that a steel frame is secured to the rear face of a GRC (Glass-Fiber Reinforce Concrete) panel with flexible anchors. The type of curtain wall has been widely used, particularly in the U.S.A., and has achieved much success.
FIG. 1 shows a perspective view of the overall shape of the same. In FIG. 1, reference numeral 1 represents a GRC panel, reference numeral 2 represents a steel stud frame, and reference numeral 3 represents flexible anchors. The characteristics of a steel stud frame type curtain wall lies in its structure so constituted that the rear face of the GRC panel 1 with a thickness on the order of 12 mm is reinforced by the steel stud frame 2, the GRC panel 1 being assumed to be similar to the surface plate of a metal curtain wall. The GRC panel 1 having a standard size surface area of 2230.times.5200 mm and the steel stud frame 2 are connected by the flexible anchors 3 which are disposed at intervals of 50 to 60 cm (FIG. 1 is used to illustrate the overall structure; therefore, the dimensions, shapes and details shown in the figure are different from those of a standard size GRC panel). The design concept of the flexible anchors 3 lies in the fact that any changes in the dimensions of the GRC panel 1 should not be restricted by the steel stud frame 2. If the GRC panel 1 is distorted by wind pressure or is thermally deformed, the flexible anchors 3 serve to absorb these changes. Therefore, it is important for the overall structure that the proof stress and reliability of the flexible anchors 3 are guaranteed.